Corrugated roof air space vs no air spac
Wormdrivehighfive
| Posted in Energy, Heating & Insulation on
Is there an advantage, especially insulation advantage, in leaving an airspace under “agricultural metal roofing” or corrugated roofing? We have put this type of roofing over plywood and tarpaper, and also on skip -sheathing depending on insulation options of the roof type (standard framing and timber-framed with finished wood ceiling. Denting is not a consideration. What do you think? Thanks in advance for your help.
Replies
I have long thought that a well designed corrugated roof is the best for longevity, maintenance and effectivness. I know you can have aluminum anodized, but I wonder if there is a good paint for galvanized.
I considered seperating the attic space and ventilating it seperately. In the attached is one way I have thought of doing this.
I have also idea'ed a mechanical way to shift venting paths to take advantage of any heat trapped in the attic.
SamT
"I have long thought that a well designed corrugated roof is the best for longevity, maintenance and effectivness."
Would you say it is even better than Standing Seam? I really would like corrugated metal for our next foor, but the exposed fasteners seem to be the weak spot.
Sounds just right the way it is, attached to a solid deck.
In the construction you described, there is little insulation value in the air space. In some instances, an air gap does provide some insulating value.
There may be no insulation value, as others have pointed out.
But there would be an advantage in that it may lessen condensation.
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quittintime
IMHO The advantages of raising the metal panels off of a deck are only fully realized if the air space is vented top and bottom. If it's vented, the convection of heated air rising will circulate air between the metal panels and roof deck that will help remove moisture and heat. If the venting is left off the bottom the air movement will be reduced and the advantage diminished. The best advantage would be realized with a furred out "cold wall" venting into a furred out "cold roof."
According to my metal supplier, metal panels applied directly to a solid surface are also more susceptible to hail dents. It seems the give of the metal panel over an air space allows it to better absorb and dissipate the impact.
Finally, the additional furring strips of lumber provide a lot more beef for your fasteners to get their teeth into. That feature is fairly important over SIP panels in high wind areas but it's not as critical over heavier decking.
Kevin Halliburton
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